Since the explosive growth in wireless communications is a worldwide phenomenon, the next generation of mobile phones, also known as 3G (third generation) or UMTS (Universal Mobile Telecommunication Services), is a technology that allows users to access e-mails, videos and webs via a mobile phone.
Many companies, such as Motorola and Samsung, have provided 3G mobile phones that possess two displays. These kinds of mobile phones offer people two viewing options. A large interior display is used for standard functions and an exterior one just shows a caller's ID or, time and date. According to this, the resolution of the interior display is much higher than the exterior one. The interior display with higher resolution is sometimes an active matrix liquid crystal display (AMLCD). The exterior display with less electrical consumption can be a passive matrix LCD (PMLCD).
A liquid crystal (LC) layer of the PMLCD is sandwiched between two glass substrates, which contain parallel sets of electrical lines (electrodes) in a row and column configuration to form a matrix. Every intersection is a pixel. When applying a voltage high enough across the pixel, the LC molecules are aligned to determine the gray scale of the pixel.
AMLCD is similar to the PMLCD. However, AMLCD further includes an electronic switch (e.g. thin film transistor; TFT) at every pixel so as to provide faster switching . The addressing mechanism eliminates problems of the viewing angle and the brightness suffered by the PMLCD.
Referring to FIG. 1, a simple comparison between the AMLCD and PMLCD is shown. The electrical consumption is much less in PMLCD than in AMLCD. The resolution and contrast ratio, however, are higher in AMLCD than in PMLCD. The manufacturability of the AMLCD is more complex than that of the PMLCD.
In order to reduce the weight and thickness of the mobile phone that has two distinct LCDs, it's beneficial to converge the active and the passive matrix modes within one LCD panel.
A reflection type liquid crystal display includes a reflective plate , that reflects the external light which enters into the liquid crystal display. The reflected external light is used as a light source of the reflection type liquid crystal display. Hence, a backlight module serving as a light source is therefore unnecessary. For this reason, the reflection type liquid crystal display is generally adopted as a display in a portable terminal device such as a mobile phone. In brief, the reflection type liquid crystal display is superior to a transmission type liquid crystal display with respect to power consumption, thickness, and weight etc.